Zalepon (CL-284846) is a novel, pyrazolopyrimidine, sedative-hypnotic which binds weakly but differentially to the GABA Brian complex. In animal models, it produced potent sedative and anticonvulsive effects similar to marketed benzodiazepines. In tests for side effect potential, zalepon, unlike most marketed sedatives, produced no hangover effect, exhibited less propensity for memory loss, reduced tolerance, (suggesting a lower potential for abuse), and at an efficacious dose showed a reduced tendency to pontentiate depressant effects with alcohol. In addition, human pharmacokinetic data predict a fast onset and elimination (t max and t1/2 are approximately 1 hour). Based on the medical need for improved sedative-hypnotics and the results of preclinical and clinical studies thus far insomnia with fewer side effects than are commonly associated with most drugs currently marketed for this purpose.